kernel: Generalize startup code into main
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parent
8d12a42442
commit
8b750aabe9
7
Makefile
7
Makefile
@ -1,7 +0,0 @@
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default: nbp.com
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%.com: %.asm
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nasm -s -o $@ $<
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clean:
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rm -f *.com
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7
kernel/Makefile
Normal file
7
kernel/Makefile
Normal file
@ -0,0 +1,7 @@
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default: kernel.com
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kernel.com: *.asm
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nasm -s -o kernel.com main.asm
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clean:
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rm -f *.com
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@ -1,3 +1,53 @@
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; assumptions about the starting envionment
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cpu 8086
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org 0x0000
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_startup:
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xor ax, ax ; trash ax
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mov ax, cs
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cmp ax, 0x0000 ; MBR or NBP, CS=0000 IP=7C00
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je .mbr
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cmp ax, 0x07C0 ; MBR on weird BIOS, CS=07C0 IP=0000
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je .mbr
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.dos:
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; ROP because call only works on immediate or memory
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mov ax, cs
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push ax ; return CS
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mov ax, .dosret
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add ax, 0x0100
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push ax ; return IP
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mov ax, cs
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add ax, 0x0010
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push ax ; main CS
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mov ax, main
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push ax ; main IP
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retf
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.dosret:
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int 0x20
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jmp .halt
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.mbr:
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push si ; index of partition table entry
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push ds ; segment for ^
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push dx ; dl might contain drive number
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push bx ; possible offset for pxeenv+ struct
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push es ; segment for ^
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mov ax, 0x0050
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mov es, ax
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mov di, 0x0000
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xor ax, ax
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mov ds, ax
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mov si, 0x7C00
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mov cx, _reloc_end
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rep movsb
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call 0x0050:main
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.halt:
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hlt
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jmp .halt
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main:
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mov ax, cs
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mov ds, ax
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@ -10,10 +60,12 @@ main:
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retf
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%include "kernel/heap.asm"
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%include "kernel/intr.asm"
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%include "kernel/debug.asm"
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%include "kernel/kprintf.asm"
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%include "heap.asm"
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%include "intr.asm"
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%include "debug.asm"
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%include "kprintf.asm"
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_reloc_end:
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align 16
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heap:
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@ -1,5 +1,5 @@
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#!/bin/sh
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exec qemu-system-x86_64 -boot n -fda fd0.img \
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exec qemu-system-x86_64 -boot n \
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-option-rom /usr/share/qemu/pxe-rtl8139.rom \
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-device e1000,netdev=mynet0,mac=52:54:00:12:34:56 \
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-netdev user,id=mynet0,net=192.168.76.0/24,dhcpstart=192.168.76.9,tftp=$PWD,bootfile=nbp.com
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-netdev user,id=mynet0,net=192.168.76.0/24,dhcpstart=192.168.76.9,tftp=$PWD,bootfile=kernel.com
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59
nbp.asm
59
nbp.asm
@ -1,59 +0,0 @@
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; assumptions about the starting envionment
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cpu 8086
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org 0x0000
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; es:bx pxeenv+ structure
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; ss:sp functional stack
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_startup:
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xor ax, ax
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mov ax, cs
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cmp ax, 0x0000 ; MBR or NBP, CS=0000 IP=7C00
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je .mbr
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cmp ax, 0x07C0 ; MBR on weird BIOS, CS=07C0 IP=0000
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je .mbr
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.dos:
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mov ax, cs
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push ax ; return CS
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mov ax, .dosret
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add ax, 0x0100
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push ax ; return IP
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mov ax, cs
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add ax, 0x0010
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push ax ; main CS
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mov ax, main
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push ax ; main IP
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retf
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.dosret:
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int 0x20
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int 0x18
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.mbr:
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mov ax, 0x0050
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mov ds, ax
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mov [0xFFFE], ss ; save current stack configuration onto new stack
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mov [0xFFFC], sp
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mov ss, ax
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mov sp, 0xFFFC
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push dx
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push bx ; possible far ptr to pxeenv+ struct
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push es
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mov es, ax ; 0x0050
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mov di, 0x0000
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xor ax, ax
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mov ds, ax
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mov si, 0x7C00
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mov cx, _reloc_end
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rep movsb
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call 0x0050:main
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.halt:
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hlt
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jmp .halt
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%include "kernel/main.asm"
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_reloc_end:
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